This is a demonstration of a system that interprets 2D mechanical
engineering designs as the user sketches them, then allows the user to see
her design in action through the use of an off-the-shelf kinematic
simulator called Working Model(tm).

The designer here is drawing a car an a hill.  Note that the designer
draws freely and the system interprets her strokes as she draws, often
having to combine more than one stroke into a single component in the
drawing, for example, the hill upon which the car sits.  The "X" on the
hill represents an anchor which fixes the body in place and keeps it from
sliding down the page due to gravity.

The designer adds wheels to the car and attaches these wheels with pivot
joints.  Note that even though both the wheels and the joints are
represented by circles, the system is able to correctly distinguish
between the two based on the context of the drawing.

The arrow on the left hand side represents gravity.

Now, we have some interpretation of what will happen when the user presses
"Run" and in fact, so does the system.

[user presses run button.]

This is an interactive system so we can add components to the drawing and
then see what effects they have had on the system's behavior.

[user presses run button again.]

The system also provides the user with several editing gestures.  To
select a piece of the system, the user circles it.  She can then delete it
by drawing a line through it....

[user deletes the anchor and again runs the system.]

... or move it my dragging it to a new location.

[user drags car.]

Finally, if the system misinterprets a piece of the sketch, for example
here where the system recognizes the newly draw wheel of the car
incorrectly as a pin joint, the user can select the "Try Again" button,
and choose her intended interpretation from among a list of possible
interpretations.